Intraoperative ultrasound-assisted peripheral nerve surgery

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Historically, peripheral nerve surgery has relied on landmarks and fairly extensive dissection for localization of both normal and pathological anatomy. High-resolution ultrasonography is a radiation-free imaging modality that can be used to directly visualize peripheral nerves and their associated pathologies prior to making an incision. It therefore helps in localization of normal and pathological anatomy, which can minimize the need for extensive exposures. The authors found intraoperative ultrasound (US) to be most useful in the management of peripheral nerve tumors and neuromas of nerve branches that are particularly small or have a deep location. This study presents the use of intraoperative US in 5 cases in an effort to illustrate some of the applications of this useful surgical adjunct.

ABBREVIATIONUS = ultrasound.

Historically, peripheral nerve surgery has relied on landmarks and fairly extensive dissection for localization of both normal and pathological anatomy. High-resolution ultrasonography is a radiation-free imaging modality that can be used to directly visualize peripheral nerves and their associated pathologies prior to making an incision. It therefore helps in localization of normal and pathological anatomy, which can minimize the need for extensive exposures. The authors found intraoperative ultrasound (US) to be most useful in the management of peripheral nerve tumors and neuromas of nerve branches that are particularly small or have a deep location. This study presents the use of intraoperative US in 5 cases in an effort to illustrate some of the applications of this useful surgical adjunct.

Historically, peripheral nerve surgery has relied on landmarks and fairly extensive dissection for localization of both normal and pathological anatomy. Surgeons can refine anatomical localization with electromyography and nerve conduction studies. More recently, MRI and ultrasound (US) have been used preoperatively as diagnostic adjuncts to limit the need for extensive dissections, particularly in cases of tumors and neuromas.4 Here, we present 5 cases in which intraoperative US was particularly helpful in localization of the pathology.

Ultrasound localization of the peripheral nerves has become commonplace in nerve blocks.11 There have been reports in the literature for some time about the use of US for preoperative diagnosis and treatment planning for peripheral nerve disorders.2 As the resolution of US has improved greatly, its clinical use has increased. Fornage was the first to systematically examine the appearance of peripheral nerves under high-resolution ultrasonography.5 A cadaveric study by Gofeld et al. demonstrated the validity of this technique.6 However, only recently has intraoperative US localization of peripheral nerves been reported.8

Several case studies report localization of difficult-to-find branches of peripheral nerves, whereas other case studies diagnose peripheral nerve tumors or compressions.3,9 The use of anatomical landmarks for the localization of peripheral nerves is currently standard practice. However, the low risk and cost of intraoperative US make this an easily accessible tool to increase the accuracy and efficiency of peripheral nerve exposures (Figs. 14). We report here the use of intraoperative US in 5 cases.

FIG. 1.
FIG. 1.

Case 1. MR image obtained preoperatively, with a vitamin E capsule adjacent to the palpable lesion, did not show pathology (A). Photograph of the right occipital area with the lesion marked and a previous craniotomy scar visible (B). Intraoperative US images obtained prior to (C) and after (D) incision to help localize the lesion show the neuroma in longitudinal (E) and transverse (F) planes. Intraoperative images of the neuroma in situ (G) and after excision (H).

FIG. 2.
FIG. 2.

Case 2. Axial T1-weighted with contrast (A) and sagittal T1-weighted (B) MR images of a neuroma (yellow arrow) of the left arm. On MRI, the neuroma was thought to arise from the median nerve. However, intraoperatively, it was found to arise from the anterior interosseous nerve. A longitudinal view (C) of the same neuroma as seen during intraoperative US, which is visualized as a hypoechoic mass with loss of the normal fascicular pattern. A more distal axial T1-weighted with contrast cut (D) of the forearm shows a neuroma of the ulnar nerve just deep to the extensor carpi ulnaris tendon. A longitudinal view (E) of the same neuroma as seen on intraoperative US. a = anterior; I = left; p = posterior; r = right.

FIG. 3.
FIG. 3.

Case 5. Intraoperative and MR Images of a man with right thigh pain. Preoperative planning of the incision using US (A). Coronal STIR (B) and T1-weighted (C) MR images along with axial STIR image (E) show an ovoid mass (yellow arrow) within the subcutaneous fat along the posterior medial right lower thigh, over the superficial aspect of the semitendinosus tendon. The mass was visualized with US (D) and excised with minimal incision (F and G). Pathological examination revealed the mass to be a schwannoma.

FIG. 4.
FIG. 4.

Operating room setup for the use of intraoperative US. The surgeon and radiologist map the prepared operative field for pathology. Cooperation and a good working relationship between the involved teams are essential for optimal results.

Case Series

Case 1: Neurofibroma of the Right Greater Occipital Nerve

A 35-year-old woman who previously underwent a craniotomy presented with a painful lump over her right occipital bone. The lesion enlarged over a period of 6 months. Intraoperative US was used to identify the lesion, which appeared to be hypoechoic, elongated, and nodular. The mass was found to be a 2 × 1–cm lesion arising from the right greater occipital nerve. The lesion was excised and the proximal end of the nerve was buried in muscle. Pathological examination revealed a neurofibroma (Fig. 1).

Case 2: Multiple Traumatic Neuromas of the Arm and Hand After a Crush Injury

A 54-year-old woman suffered a crush injury, resulting in partial amputation of her left hand 12 years prior to presentation to our clinic. She previously underwent 2 resections of neuroma 2–3 years after her injury. She presented to our clinic with extreme hyperalgesia, allodynia, and phantom limb pain. MRI done prior to surgery showed multiple neuromas in multiple peripheral nerve distributions (Fig. 2). Intraoperative US was used to guide dissection for a total of 8 neuromas. One large neuroma was identified as a hypoechoic mass arising from the anterior interosseous nerve in the forearm, which was treated with external neurolysis, fascicle splitting, and grafting, with intramuscular transposition. Two lesions were found arising from the ulnar nerve near Guyon’s canal, which were also treated with external neurolysis, fascicle splitting, and grafting, followed by intramuscular transposition. Two smaller dorsal digital neuromas and 3 small volar digital neuromas were also excised.

Case 3: Medial and Lateral Sural Neuromas

A 42-year-old man (a drummer) presented with pain, claudication, and cramping in his right leg. He previously underwent fasciotomy. Intraoperative US was used to localize 2 lesions, 1 arising from the medial sural nerve and 1 arising from the lateral sural nerve; both were hypoechoic and showed loss of fascicular pattern. Both were treated with excision and intramuscular transposition.

Case 4: Iatrogenic Ilioinguinal Nerve Injury

A 52-year-old man had an inguinal hernia repaired with mesh 16 years prior to presentation to our clinic. He had experienced progressive pain in the region, which had now become disabling. On physical examination, he was found to have a positive Tinel’s sign on the medial aspect of the scar and was taken to surgery. Intraoperative US was used to identify a 5-mm hypoechoic nodular mass in the area of his previous surgery and to guide dissection down to the right ilioinguinal nerve. A Prolene (Ethicon) stitch was found through the neuroma, which was treated with excision and intramuscular transposition.

Case 5: Cutaneous Nerve of Thigh schwannoma

A 44-year-old man had pain in his right popliteal fossa. Five years earlier, he had experienced the same pain and 2 schwannomas were removed from his right calf; a third was left behind because the prior surgeon found it “attached to a nerve.” We re-explored the area, using intraoperative US for guidance (Fig. 3). Attached to a cutaneous nerve was a rounded hypoechoic nodule, which was treated with excision, while preserving the parent nerve. Pathology revealed the mass to be a schwannoma. Figure 4 shows the setup of the operating room with the US machine and radiologist.

Discussion

Minimal-access surgery is an important aspect of today’s neurosurgical practice. In the brain, intraoperative localization of small and deep lesions relies heavily on stealth MRI navigation, stereotaxy and, to a lesser extent, intraoperative US. In the spine, accurate placement of pedicle screws relies on either stealth CT navigation or intraoperative fluoroscopy. Stealth navigation is only possible when there is a fixed relationship between the navigation frame and the target. This is not feasible when working on extremities, due to their high mobility (multiple joints) and easy distortion of soft tissues with dissection and retraction. We find intraoperative US particularly useful in the management of peripheral nerve tumors and neuromas of nerve branches that are particularly small or have a deep location. Localization by palpation or correlation with preoperative diagnostic studies may be adequate in large and superficial lesions. However, surgical targets that are deep seated, multiple, and complex may not be amenable to surface localization at the time of surgery. Additionally, in cases of traumatic and iatrogenic neuromas, scarring can be a formidable adversary that increases operative time, extent of dissection, and frustration. The cases presented here demonstrate the use of the intraoperative US technique.

Multiple neuromas were resected in Cases 2 and 3; intraoperative US was helpful for incision planning, localization of the parent nerves, and identifying the multiple neuromas. In these cases, the use of intraoperative US immediately after resection was able to confirm resection of all neuromas prior to closing. In Case 2 in particular, the patient had significant allodynia and would not allow anybody to touch her hand while she was awake, which rendered preoperative localization by palpation or US impossible. Intraoperative mapping under general anesthesia allowed accurate localization and resection of 8 neuromas. It is worth mentioning that successful surgical technique, including localization, equals good outcomes. The patient’s pain and allodynia significantly improved to the point that 3 months after surgery, she was asking about getting a prosthetic hand.

In Cases 1, 3, 4, and 5, we explored previous operative beds, dealing with abnormal planes related to postoperative scarring. It is for these cases that intraoperative US has been particularly helpful in identifying normal neurovascular and muscular structures, identifying pathology, and limiting the dissection necessary to perform safe and adequate surgery. In Case 4 in particular, finding the ilioinguinal nerve (which is very small) within a mass of scar tissue without any intraoperative guidance would have been very challenging and frustrating.

From a technical standpoint, to optimize US imaging, the highest-frequency US probe possible should be used. However, high-frequency probes have less deep-tissue penetration. The choice of probe, therefore, depends on the depth of the pathology. As summarized nicely by Koenig et al., superficial lesions, such as the median nerve, should be examined with 15–18-MHz transducers, whereas deep nerves, such as the sciatic nerve or the brachial plexus, are better examined with 9–12-MHz transducers.7

The US appearance of peripheral nerves is typically dark nerve (hypoechoic) seen on a bright (hyperechoic) background.1 Often the nerve itself will have a fascicular echotexture, which can help differentiate it from tendons, which have a more fibrillar texture.10 The quality of the US machine is also key in obtaining high-resolution imaging.

One challenge to the use of intraoperative US is the availability and willingness of an experienced radiologist and/or technician to come to the operating room. This factor can be mitigated as the surgeon gains familiarity with ultrasonographic appearance of nerves and lesions, as well as the technical nuances of using a US machine.

Conclusions

Minimally invasive surgical approaches are appealing to patients and surgeons. In peripheral nerve surgery, refining the localization of normal and pathological anatomy can minimize the need for extensive exposures, decrease incision size, improve cosmesis, decrease operative time, reduce postoperative pain, and improve patient and surgeon satisfaction. We find it particularly useful when dealing with multiple lesions, small lesions, deep or difficult-to-localize nerves, and in scarred operative beds, whether from previous surgery or trauma. Similar to the emergence of electrophysiology as standard practice in peripheral nerve diagnosis and stealth navigation in localizing deeply seated brain tumors, it is probable that the use of intraoperative US assistance will gain comparable traction.

Looking forward, neurosurgeons will benefit from a detailed understanding of the ultrasonic anatomy of the peripheral nerves and the associated pathologies. Improvements in technology have made US increasingly useful as a real-time imaging modality. High-resolution US can define not only nerves and pathology, but also intra-neural anatomy. The ultrasonographic fascicular anatomy, which has become substantially more important in the era of nerve transfers, will be an element of peripheral nerve surgery that trainees and experienced surgeons alike will not be able to overlook.

The cases presented here demonstrate the situations that are particularly amenable to intraoperative US assistance. We have found that the low risk, low cost, and ease of intraoperative US assistance are beneficial to both surgeon and patient.

Author Contributions

Conception and design: Hanna, Haldeman. Analysis and interpretation of data: all authors. Drafting the article: all authors. Critically revising the article: all authors. Approved the final version of the manuscript on behalf of all authors: Hanna. Administrative/technical/material support: Haldeman.

References

  • 1

    Beggs I: Pictorial review: imaging of peripheral nerve tumours. Clin Radiol 52:8171997

  • 2

    Buchberger WJudmaier WBirbamer GLener MSchmidauer C: Carpal tunnel syndrome: diagnosis with high-resolution sonography. AJR Am J Roentgenol 159:7937981992

    • Search Google Scholar
    • Export Citation
  • 3

    Chiou HJChou YHChiou SYLiu JBChang CY: Peripheral nerve lesions: role of high-resolution US. Radiographics 23:e152003

  • 4

    Du RAuguste KIChin CTEngstrom JWWeinstein PR: Magnetic resonance neurography for the evaluation of peripheral nerve, brachial plexus and nerve root disorders. J Neurosurg 112:3623712010

    • Search Google Scholar
    • Export Citation
  • 5

    Fornage BD: Peripheral nerves of the extremities: imaging with US. Radiology 167:1791821988

  • 6

    Gofeld MBristow SJChiu SKliot M: Preoperative ultrasound-guided mapping of peripheral nerves. J Neurosurg 119:7097132013

  • 7

    Koenig RWPedro MTHeinen CPSchmidt TRichter HPAntoniadis G: High-resolution ultrasonography in evaluating peripheral nerve entrapment and trauma. Neurosurg Focus 26:2E132009

    • Search Google Scholar
    • Export Citation
  • 8

    Koenig RWSchmidt TEHeinen CPWirtz CRKretschmer TAntoniadis G: Intraoperative high-resolution ultrasound: a new technique in the management of peripheral nerve disorders. J Neurosurg 114:5145212011

    • Search Google Scholar
    • Export Citation
  • 9

    Lee FCSingh HNazarian LNRatliff JK: High-resolution ultrasonography in the diagnosis and intraoperative management of peripheral nerve lesions. J Neurosurg 114:2062112011

    • Search Google Scholar
    • Export Citation
  • 10

    Silvestri EMartinoli CDerchi LEBertolotto MChiaramondia MRosenberg I: Echotexture of peripheral nerves: correlation between US and histologic findings and criteria to differentiate tendons. Radiology 197:2912961995

    • Search Google Scholar
    • Export Citation
  • 11

    Walker KJMcGrattan KAas-Eng KSmith AF: Ultrasound guidance for peripheral nerve blockade. Cochrane Database Syst Rev 4CD0064592009

    • Search Google Scholar
    • Export Citation

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Article Information

Correspondence Amgad S. Hanna, Department of Neurological Surgery, University of Wisconsin Hospitals and Clinics, 600 Highland Ave., K4/822, Madison, WI 53705. email: ah2904@yahoo.com.

INCLUDE WHEN CITING DOI: 10.3171/2015.6.FOCUS15232.

Disclosure The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

© AANS, except where prohibited by US copyright law.

Headings

Figures

  • View in gallery

    Case 1. MR image obtained preoperatively, with a vitamin E capsule adjacent to the palpable lesion, did not show pathology (A). Photograph of the right occipital area with the lesion marked and a previous craniotomy scar visible (B). Intraoperative US images obtained prior to (C) and after (D) incision to help localize the lesion show the neuroma in longitudinal (E) and transverse (F) planes. Intraoperative images of the neuroma in situ (G) and after excision (H).

  • View in gallery

    Case 2. Axial T1-weighted with contrast (A) and sagittal T1-weighted (B) MR images of a neuroma (yellow arrow) of the left arm. On MRI, the neuroma was thought to arise from the median nerve. However, intraoperatively, it was found to arise from the anterior interosseous nerve. A longitudinal view (C) of the same neuroma as seen during intraoperative US, which is visualized as a hypoechoic mass with loss of the normal fascicular pattern. A more distal axial T1-weighted with contrast cut (D) of the forearm shows a neuroma of the ulnar nerve just deep to the extensor carpi ulnaris tendon. A longitudinal view (E) of the same neuroma as seen on intraoperative US. a = anterior; I = left; p = posterior; r = right.

  • View in gallery

    Case 5. Intraoperative and MR Images of a man with right thigh pain. Preoperative planning of the incision using US (A). Coronal STIR (B) and T1-weighted (C) MR images along with axial STIR image (E) show an ovoid mass (yellow arrow) within the subcutaneous fat along the posterior medial right lower thigh, over the superficial aspect of the semitendinosus tendon. The mass was visualized with US (D) and excised with minimal incision (F and G). Pathological examination revealed the mass to be a schwannoma.

  • View in gallery

    Operating room setup for the use of intraoperative US. The surgeon and radiologist map the prepared operative field for pathology. Cooperation and a good working relationship between the involved teams are essential for optimal results.

References

  • 1

    Beggs I: Pictorial review: imaging of peripheral nerve tumours. Clin Radiol 52:8171997

  • 2

    Buchberger WJudmaier WBirbamer GLener MSchmidauer C: Carpal tunnel syndrome: diagnosis with high-resolution sonography. AJR Am J Roentgenol 159:7937981992

    • Search Google Scholar
    • Export Citation
  • 3

    Chiou HJChou YHChiou SYLiu JBChang CY: Peripheral nerve lesions: role of high-resolution US. Radiographics 23:e152003

  • 4

    Du RAuguste KIChin CTEngstrom JWWeinstein PR: Magnetic resonance neurography for the evaluation of peripheral nerve, brachial plexus and nerve root disorders. J Neurosurg 112:3623712010

    • Search Google Scholar
    • Export Citation
  • 5

    Fornage BD: Peripheral nerves of the extremities: imaging with US. Radiology 167:1791821988

  • 6

    Gofeld MBristow SJChiu SKliot M: Preoperative ultrasound-guided mapping of peripheral nerves. J Neurosurg 119:7097132013

  • 7

    Koenig RWPedro MTHeinen CPSchmidt TRichter HPAntoniadis G: High-resolution ultrasonography in evaluating peripheral nerve entrapment and trauma. Neurosurg Focus 26:2E132009

    • Search Google Scholar
    • Export Citation
  • 8

    Koenig RWSchmidt TEHeinen CPWirtz CRKretschmer TAntoniadis G: Intraoperative high-resolution ultrasound: a new technique in the management of peripheral nerve disorders. J Neurosurg 114:5145212011

    • Search Google Scholar
    • Export Citation
  • 9

    Lee FCSingh HNazarian LNRatliff JK: High-resolution ultrasonography in the diagnosis and intraoperative management of peripheral nerve lesions. J Neurosurg 114:2062112011

    • Search Google Scholar
    • Export Citation
  • 10

    Silvestri EMartinoli CDerchi LEBertolotto MChiaramondia MRosenberg I: Echotexture of peripheral nerves: correlation between US and histologic findings and criteria to differentiate tendons. Radiology 197:2912961995

    • Search Google Scholar
    • Export Citation
  • 11

    Walker KJMcGrattan KAas-Eng KSmith AF: Ultrasound guidance for peripheral nerve blockade. Cochrane Database Syst Rev 4CD0064592009

    • Search Google Scholar
    • Export Citation

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